Accumulator



Dec. 22, 1953 R. E. SNYDER 2,663,320

ACCUMULATOR Filed Nov. 18, 1946 2 Sheets-Sheet l R. E. SNYDER v ACCUMULATOR Dec. 22, 1953 2 Sheets-Sheet 2 Filed Nov. 18, 1946 FIG. 4.

Y. 2 M M y .2 N w 5% m if P.

Patented Dec. 22, 1953 UNITED STATES ATENT O FF ICE.

AC CUMULATOR'.

ApplicatiomNovember- 18, 19.46, S.erialNo.:.7:1fl,490

(Cl. 1383I) '14 Claims. I

My invention relates .to thaart. of. hydraulic pressure storage: tanks,..-more :commonly known as: pneumatic; hydraulic: accumulatorsin -ac.-- cumulators. of. thisv type; hydraulic fluid is :stored under the; pressure. produced by a compressed gas. within a common: container. Moreparticularly inventionrelates .to-animproved. means for separating, ibhaliWO: fluid .media, compensation for large pressure.--.cha-nges, and thertransierring otminute pressure variation.- in-the liquid to gas: and. vice versa.

In order to avoidintermixtureand/or absorption. of. the gas: into. the liquid,:hydraulic accumulators; commonly employ "separating. meansbe! tween the two fluids; such as, for example adiaphragnra. bellows, 'a bag or a; piston. Thus fluid pressure on. one side: of' the separating means is. readily transferred: .to. the: fluidon. .theopposite. side. Each of -.the. alonvc-describedv separating means has its preferred-use andeachphascertain inherent limitations.

The diaphragm or bagtypes. are extremely sensitive to. minute pressure changes due to. the relatively low weight and the low inertia factor of the relatively thin membranes from which they can. be made. Membrane: separators have the-common. failing, however, of being relatively large in area and thereforesubject to. certain destructive. mechanical stressesator 'neartheir extreme positions. Moreover; they "are. weakened byycontinued: :creasing: or folding and they may be torn or pierced. quite. easily,qth.eir-.larg e. area increasing the chance-oi: such damage or puncture.

The piston type, :on the. other hand, easily moves thefull length of the hydraulic accumulator to adjust for any desired pressure. It is rugged and not easily damaged. However, its relatively greater weight introduces an inertia factor whichmakes it less. sensitivetominute pressure variation. The-necessary frictional engagement-between hydraulic pistons and cylinder walls makes the piston 'slow'to. respond'to rapid pressure. changes; Many other; inherent differences between theabove: types of accumulators will occur to those familiarwith the-art.

The present invention. contemplates major improvement of the: piston: typer accumulator in which the primary object is to ccmioine the sensitivity of the diaphragm,ibellowsg orthag type with the indefinitely large.- range ofgpressure 'variat'i'on 'of"the' piston type accumulator: In; the present invention, apiston 'i's provided. which is free ":to movethe full length :of an accumulator eyl inder'to ad jrust for anymajfo'r pressure change between'thegas and the. liquid, and'a diaphragm. or. flexiblewelement provided and is free .to flutter. in response. to. .minuta pressure or volume variations which, in conventional accumulators, would not move the piston itself.

One object of. my invention is. to. provide an accumulator having both apiston and diaphragm as. described. and wherein the diaphragm is mountedin the piston itself and-moves there.- with, thus making for economical manufacture and ease of assembly and. maintenance.

An additional object-army invention, as an alternate form, is to provide a tubular type; dia-- phragm; in the side of. a-piston. whereby to achieve full sensitivity to small pressure. variations while permittingdirect, unobstructed flow through the liquid inletport of the accumulator cylinder.

Still another .objectzristo. provide protective means 1 for the diaphragm. whenthere is no liquid I intheaccumulator, whereby to support the same so thatthe prechargepressure normally provided in the gas chamber will not extrudeor damage the sensitive diaphragm. In both hag anddiaphragm accumulators of conventional. design it is. common practice to cover. theliquid outlet port through the shell with a. screen or orificedr plate to prevent-extrusion of thebag or diaphragm when. the liquid pressure falls below the precharge pressure. Such a plate or screen in the shell: often is undesirable however, since it. forms annbstruction to. the free flow ofv liquid into-or out of .theaccumulator. The present invention provides. a smooth metalwall, to support.- the; diaphragm-v duringthe minimumpressure condition, the diaphragm: being heldv insome cases in a. position out of line withtheliquid-orifice hence not-obstructing the same; This support means iorthe diaphragm may be adapted ior either the fiat or the tubular. diaphragms alcovedescribed as well: asior any alternate construction.

A .further object: is to provide a, cheap and eiiicient. structure. which iseasy to assemble and service; and which may .be constructed with any safety factor necessary-for its projected use.

'Theseand, other objects of. thepresent invention. will become apparent from the following description or several preferred, forms thereof, and from. the drawings. illustrating these forms in which:

Fig; 1 isa'diagrammatic elevational section of an :accumulator embodying my invention, illustrative of thebasicprinciples thereof, and shown a. 1 precha-rged position .2 a section td-Eig. .1, showing the: device -:an;. operative 3 position Fig. 3 is a longitudinal vertical section of a preferred form of the accumulator having a substantially plate type diaphragm and with cer- 1tain parts cut away to show the internal strucure;

Fig. 4 is a similar view of another modified structure in which a tubular diaphragm is used in the piston and the liquid port is modified to accommodate it; and

Fig. is a horizontal section taken along the line 55 in Fig. 4.

Referring now to the drawings and particularly Figs. 1 and 2 thereof, the fundamental principles of operation of my invention may be clearly understood. The numeral I indicates a hydraulic cylinder having a smooth interior bore in which a piston 3 is slidably supported and is free to move from one end of the cylinder I to the other, being limited in its motion by the end walls of the cylinder. A flexible cup-shaped diaphragm 4 is secured at one end of the cylinder I and enclosed in a chamber defined by spheroidally-shaped walls 5 and 6. The spaces to the left of the diaphragm 4 and to the right of the piston 3 are interconnected by means of a plurality of openings me. These two spaces constitute a gas chamber which is adapted to be charged through a threaded nipple 2 projecting from the side of the cylinder I. When the desired precharge pressure has been produced in the gas chamber, the nipple 2 is hermetically closed as indicated schematically by the screw cap I02.

The accumulator illustrated in Figs. 1 and 2 is adapted to receiv liquid in spaces to the left of the piston 3 and to the right of the diaphragm 4 such liquid being delivered by a pair of endconnected ducts 8 and I08, respectively, which are joined to a common duct 203 for connection to a hydraulic system. Since the fluid chambers just described are interconnected they may, in effect, be considered as one chamber. Thus the accumulator shown in Figs. 1 and 2 is to be considered as having hermetically separated chambers, one adapted to receive fluid and one containing gas under pressure.

Fluid pressure in the above hydraulic system will force liquid into the liquid chamber above described causing the piston 3 to move to the right and the diaphragm 4 to move to the left thus compressing the gas in the gas chamber. The only pressure differential existing on the two sides of the diaphragm 4 is that occasioned by the differential pressure on the two sides of the piston 3 occasioned by the frictional drag thereof on the walls of cylinder I.

The walls 5 and 6 of the diaphragm chamber are so formed as to provide a smooth support for the diaphragm in either of its limited positions. As shown in Fig. l, the diaphragm is forced against the wall 5 by the precharge pressure in the gas chamber there being no fluid pressure exerted on the right side of the diaphragm. By virtue of the fact that a plurality of relatively small openings are provided at I05 and at I65, there is no tendency for the diaphragm ii to be extruded into these openings when the diaphragm is supported either by the wall 5 or the wall 6.

As can be seen from an examination of Fig. 2, motion of the piston 3 within the cylinder I compensates for large changes in pressure of the fluid system connected at the ducts 208 while small fluctuations in pressure are compensated for by relatively small changes in the volume of d the gas chamber permitted by fluttering or fluctuating motion of the diaphragm 4.

By reference now to Fig. 3 it will be seen that one preferred embodiment of the present invention employs a body 9 comprised of a tubular shell I0 having each end closed with plugs ii and I2 affixed therein as end closures and provided with a piston I3 slidable in said shell between said end plugs. The piston IS divides the body 9 into two separate and dependently vari able chambers I1 and I8; the chamber i'l being above the piston I3 and the chamber It being below the piston I3 within body 9 so that any movement of piston is varies chambers Ill and It in a supplemental manner, one gaining such volume as the other loses. The shell iii may be constructed from seamless steel tubing of sufficient length to provide the required capacity of the accumulator and having its bore i l finished smooth as, for example, by lapping or honing, to provide a suitabl internal surface for the piston I3 to ride upon and seal against. It should be noted further that the wall thickness of the shell Ill while suflicient to withstand the working pressure of the accumulator, should not be thin enough to bulge outwardly under such working pressure and thereby permit gas or liquid to seep past the piston in either direction. The plug II located at the gas end of the accumulator may be affixed within shell It in any suitable manner provided a leakproof seal is established. In the form shown in Fig. 3 the plug II is provided with an annular groove 55 in which a packer seal I6 is positioned between the plug I I and the bore I4 of the shell it. This sealing packer It may be of any desired type such as an O ring, a chevron packer, or any other suitable means unaffected by the fluid and capable of withstanding the temperatures and/ or pressure required in the use of the accumulator.

The plug H is locked into the shell in by the use of a split shear ring 2t seated in an annular groove 2: in the bore I iinwardly from the end 22 of the shell it. The shear ring as is divided into three or more sectors so that it may pass through bore E i and be placed in the groove iii of the shell. A complementally shaped shoulder 23 located on the plug l I outwardly from packer it provides an abutment for plug iI against shear ring 28 and the inner wall 2 above shoulder 23 holds the shear ring 2% in the groove 2i. An orificed bolt plate 2? is provided to abut the outer end 22 of the shell Iii and has a plurality of holes 28 drilled therethrough. correspondingly placed holes 29 are bored and threaded in the plug II so that bolts 3%! placed in the holes 23 and threadedly engaged in the plug l I may be drawn up tight to hold the plug ii shouldered against the shear ring in the groove 2i and lock both the plug II and the bolt plate 27 securely to the end of shell It. The removal of bolts to will permit the plug I I to be slipped down inside the shell H3, permitting removal of the shear ring 2i! from the groove 2i, and complete disassembly of the plug I I and the shell ill. It will be evident that other methods of attaching the plug It to the shell It may be used such as threading, welding, keying, etc., and that the means shown is illustrative only.

The plug I I is provided with a domed internal face 35 having a hole 35 extending therefrom to the outside of the plug II. Threadedly secured in the hole 35 is a gas inlet pipe 37 with a suitable valve 38 and gas control means (not shown) at tached thereto. The pipe 31 extends from the assessmpiue l i through an openim; 3e ilflitlTErfiO'lt plate? 2 Tto the outside of the-accumulator;-

The opposite end iii of= the=shel1 I it is 'provitiedsj withaplug l which; while it may-"be attachechto I shelll 6 inany] suitable manner, is-preferably at taehed theret'o in a= similar mannen to the plug: i i The plug I2 is -comprised-essentially: of ascenti'al body' portion- 4 in the cylindrical surface of which isformed"anannularpaokinggreet/e 42? A packing ring 53-, substantially the sameizas th'epacker i5 used in-.-th'eplug: H =i's seatedin". the; groove TF2? to seal theintersticebetween-the plug I2 and the=bore i i 'of theshell l 1- A' secondbolti 1312113814 3; a= split'ring efi-i and bolts -it are used-to lock-7 the plug (2 into the shell 18; A neck; $8 extends outwardly from the body portion-- 4'! through aniopjening 3? the=bolt plate: is; neck $8 is" threaded as shown or may; be flanged:v orotherwiseprovided with means for attachment to a" sourceofliouid'i The opp'o'siteend' 55 of the plug it extendsfoi" a substantial distance inwardly of the central body portion il a-nd'is provided with'a supporting face 56'' for a" piston diaphragm 9'? to be described: presently. This inwardly extending"portion-5511s formed' withtaperedsides 5T which are substan tially complemental to-the bore" it et: the: pistonl3.

lnwardly fi'om grooveszl and at thebase 58 0f the inwardly extending portion 523 ofthe'plug' 12.

between the piston is and the shoulder as:

Thus thebody 9 of the accumulator has open'- ings'in the end plugs I i and" I2 for-theentrance of gas into the'chamber H and of liquid into the chamber It on their respective'sides of the piston I3:

Asa general rule atleast one of theplugs- H or: l2 should be" removably attached. to shell" le so thatitsremoval will permitremovalof piston" 13 from shell itl In Fig; 3; botl'i plugs' and I2" are attached to and sealed againstshell It? by identical and either or both be removed. Selection of a construction permitting: the removal of the plug H, the plug IZ or'b'oth. plugs depends upon the desire of the manufacturer, theparticular use to w-hich'the accumu'- later is to be put; and the attendant structure with which. it must be operated. V

The piston: {3 is comprised essentially oi? a:

' cylindrical 1000157 "F 9 and: has -a; flexible; diaphragm:

'li. mounted in theupper end 72 thereof: As stated, the b'ore- 53 ofthespistonzistapered sub;- stantially complementally to the taper-tTon'the'i plug !2. The lower'endiof the piston: ittformsi a skirt with a flat facefi 'liwhich istadapted' to? abut l andrest on the shoulder. 5% of the. plug it? When in the extreme downward position. With: the piston l 32in this :restzposition, sufii'cicnt clearance is provided'i'between'its bore '53.: and tapered? face 57iof' p'lug 2 to avoid;stickingroirseizure, and? the upper end lE'of theibore. lfli'isisubstantially in alignment withithe? face 55L of plug? [2: The:

. sealrtheinterstice' 88 betweenpthe'pistonandbore his Betweemthepacking.grooves:3 and Blithe 0111381'."N3J11L0f$ theskirtof .the' piston .13 is relieved toiprovide aachamber 39.. useful. as. a: pocket; for. oil to lubricate thepiston; OillQiLor other-suit.--. able-.lubri'cantr. may; if desired, heplaced in ,this: space; Bleediho'les .9 Exfrom. theichambeni ."i above. theepiston; 3rleading: behindgthes packing 8 5.. and. opening:intothechamber. 89 seryeto balancethe; pressureiofs. thezgvas; inxthe, chamber i above :the

piston .532 with that in;the chamber 88. The-her.

metici seal-.betweenthe' gasin; the chamber: I above the; piston. .l 3.: and the fluid. in. the chamber iiiibelow: the piston is eifectedrby the lower packer tlf-whiletheiuppeipacker. 8t. merely serves to iii...

piston !3.

the. accumulator werea lubricantliquid; bleed holes 95 might be omitted anda'. second set. of bleed? holes: (not? shown)- between. chamber 53 below the piston 23' anclLchamber 89:0ou1dbesubstitutedz. In: thisslatter." case the seal wouldbe effected. the upper: packing 8i; leaving the lower 'packer'tTt'o serveito alignand position the- One or'the other set cf'bleed holes should alwaysi'bezused'to avoid the entrapment" of gasor' liquid under pressure in chamber 59. which in turn could result in sticking'of the piston. at: low gas and/ or -liquidrpressures;

A'spreviouslystatedithe diaphragm .lfi mount:- ed'inthetpiston: i'tirests uponand' is supported by'the convex face; 561': of'the' plug: l2. when the; piston is inzthelowerm'ost position. The fitbeitween the plug" l2andthe piston itadjaoent'thei diaphragm is 1 closeenough to" avoid: any. damage. to or extrusion of the diaphragm uncler the precharge'gas'pressure in the chamber 1?; At any other position When'the liquid. in the chamber i8. on: thelower side of the diaphragm counter balances the gas pressure in the chamber llabovet the piston,- the diaphragm serves" as a virtually weightless; non-resistant membrane fioatingibetween; andseparating the respective fiuids, and: is iurthermore;-. extremeiy 'sensitive to slight volume variations'in eitherthe-gas or the liquidside with negligihleinertiaor frictional resistance to. movement: Thus largechanges in the volume ratio'between the gas chamber i l and the liquid chamber It arecompensatecl for by motion up or down ofjthepiston It, and'small volume changes are comp-ensatedi'for.by movement of the dia-- p'h'ragm Ti 'Withinthe'piston' l 3'.

The. diaphragm .H is. formedwith. a base ring; 96, to which is fastened thedome shaped diaphragm...sheet.ill, the entireuuniti-being secured inthepiston. :3. by, a. snap ring 9.3; Thereare obviously-:2u number of alternate..methods of attaching. the, diaphragm? to the. piston, any of which,.including direct sbonding'ofthe diaphragm sheet t-Ttotheyoorly; of the piston i3 itself, may housed-within. the-scope of the present invention. Leakage around the edge of the diaphragm H from'therchamben i!- tothe chamber i-Sarounrlthe 1 piston 1:2,..01 vice. versa;. can be prevented by' "3 the use of suitable cement, packers or other means (not shown) as required.

In the present form of my invention the base ring 96 is made of metal and the diaphragm sheet s1 is a synthetic rubber such as Hycar, neoprene, or similar material, which is bonded directly to the metal itself with one or another of the commercial processes for such bonding known in the art.

The diaphragm sheet ti is of sufficient strength so as (when in an extended position shown) to easily move the piston I3 against the friction of the piston packers 38 and til against the walls of the bore M. Furthermore the diaphragm is sufiiciently flexible to move freely in response to very minute pressure changes, has a low inertia factor and is tough and relatively unstressed within the normal range of movement. By reason of the previously mentioned close fit between the plug l2 and the piston 13, the diaphragm is not forced into the space between these two parts even by high gas precharge pressures and is substantially unaiiected by any liquids with which it must come in contact. In some cases an elastic material may be used or in others an inelastic material. However, a wide departure from these presently preferred specifications can be made without departing from the scope of the present invention.

By reference to the alternate position of the diaphragm shown in dotted lines, one example of the possible range of movement may be seen. A molded cup-type diaphragm substantially as shown and used in a standard six inch accumulater, provides a volume change or" 8.5 cubic inches when moved from one extreme position to the other without any motion whatsoever on the part of the piston itself.

The molded cup is moved from one extreme position to the other with minimum elastic stretch, because or its normal preformed shape. In any event the exact shape, size, thickness, material, and contour of the diaphragm may be varied from fiat to globular to meet whatever requirements seem necessary in the particular accumulator. The resultant shape of the supporting faces as for example face 55 on plug I2 will be determined by that found best for the particular shape of diaphragm used. The convex supporting surface shown in Fig. 3 on plug I2 is but one possible form which has been found useful with the cup-shaped diaphragm II. In general, a diaphragm of the type shown in Fig. 3 mounted in the piston substantially as shown will be referred to as a fiat diaphragm while the form shown in Fig. 4 will be referred to as a tubular diaphragm. In fact all possible forms of flexible or readily deformable membranes or walls including closed bags, open bags, bellows and Syl phon types, semi-bag types such as the cup dia phragm shown in Fig. 3 as well as completely flat types constructed of synthetic rubber, metal, or any other suitable material will all be included in the broad term, diaphragm, as used in the specification and claims hereof.

Figs. 4 and 5 illustrate a further modification of the structure of Fig. 3 wherein a diaphragm IlI in a modified piston H3 is substantially tubular in shape and is located in the sides of the piston H3 instead of in the top as in the form shown in Fig. 3. In this modification the body we of the accumulator is comprised of a tubular shell I!!! having end plugs Ill and H2 afhxable therein in any suitable manner but shown the same as in Fig. 3. The piston H3 is positioned in bore H4 of shell Ht in the same manner as the previously described embodiment and divides body I09 into two chambers EI'! and H3, respectively, above and below the piston H3. As before, both plugs and piston are provided with sealing means against leakage in the manner previously described. There are, however, several changes in the lower plug H2 and in the piston I I3 to meet the requirements of the tubular type diaphragm I II in contradistinction to those required for the flat type diaphragm.

Primarily the plug I I '2 has a bore I65 completely therethrough from its outer end M8 to its inner face I56. There are no cross bores for fluid, only the small bleed hole It! still being provided to prevent entrapment of fluid. The plug H2 is provided with a shoulder I59 at the base I58 of the inwardly extending portion I55 upon which the piston IIZ may rest when in the extreme downward position. The sides of the inwardly extending portion I55 are smoothly tapered as indicated by the numeral I57 to conform to the bore I13 of the unstressed diaphragm HI, and the upper face I55 of plug H2 is substantially fiat to conform to the inside face Ilt of the piston H3. Thus fluid entering the accumulator through the bore I65 passes directly up inside of or toward the bore I13 of the piston i it.

The piston H3 is comprised essentially of an upper portion I'ls and a lower portion I'Ie which two portions are rigidly joined by a plurality of webs IIB which form a webbed skirt. Packing grooves I8I and I82 are formed in the outer surface of both upper and lower portions, respectively, of the piston H2 in which packers m8 and i8; are suitably disposed to ride against the walls of the bore H4 to seal the piston us within the shell I It in substantially the same manner as that described for the piston It in Fig. 3. In the webbed skirt of the piston H3 between the upper and lower portions I18 and HS, and inside the webs I10, the tubular diaphragm ili is afiixed by any suitable method to said upper and lower portions, for example by bonding to the metal so that the diaphragm is firmly held and no leakage is permitted. An annular chamber 235 is provided surrounding the diaphragm and communicates with the gas chamber Il'i above the piston I I 3 by one of more bleed holes 95 through which the gas may circulate to equalize the pressure between the two chambers II? and ISQ. Fluid or other lubricant I98 may optionally be placed in the chamber I89 to lubricate the packers I86 and I8! used in the piston.

The inside face H3 of the diaphragm I'ii is relatively smooth and adapted to seat against the tapered portion I5! of the plug IIZ. In the extreme downward position of the piston lit when its lower face I84 is resting against the shoulder I59 the upper face see of the plug 522 rests substantially against the inside upper face N8 of the piston M3, the diaphragm ill being supported by the tapered portion 15? of the plug and hence protected from extrusion or damage by the precharge gas pressure in the chambers I I1 and I89. In any other position the liquid pressure in the chamber H8 on the inside of piston H2 counterbalances the gas pressure on the outside of diaphragm Ii! in the chambers I89 and Ill.

The tubular diaphragm I'll is free to bulge radially from an inward position as shown in solid lines to an outward position as shown in dotted lines in Figs. 4 and 5. The volume variation due to this motion of the tubular diaphragm is greater than; the equivalent motion. of thefiat diaphragm type shownin Fig. 3 becausetheside wall area-of a pistonis usually larger tha,-n..the end area. However, its actionlin'responsetosmall pressure variations is substantially; the-sameas in the fiat diaphragm-type; Infan extreme-case if the piston should stick,- the hydraulicpressure could press the tubular diaphragm llftloutlagainst the walls of bore l i i. The-lubricant team the chamber i823 would lubricate anygcontaot-ofidiaphragm ll"! against the walls ofil-shellull tvand no damagewould result.

The terms pneumatic-hydraulicaccumulae tor, accumulator, or hydraulic accumulator? are used interchangeably: hereirrto designate a 7 unit designed to store hydraulicziiuidunder pres= sure as; a reserve. power source; onto iabsorbrand suppress fluid volume variations or" hydraulic surge. in asystem whichuin turnzlwouldmausena pressureivariation in that system;

In; the oil. industry andzelsewherea; dere signed to relieve hydraulicssurge: isizcommonly called an alleviator.. Such: atunit -wor-k'sz as a relief valve toallow theiescape ot fluid surges which tend to .raise the. pressureain. a: system. However, they must hgresetfor everydiffierent lineworking pressure, anddonot absorbsuch surges. and: feed; them back. into the line during the below-average; pressure-ilevels of the: surge cycle, but merely bleed oiT excess fluid toeliminate any excess whichnwouldi cause pressures abore that required. Thexinertia factors of conventional. alleviatorsxare usually much too high to respond to. vibrational pressure surges although theyrare quitefusef-ul on very slow 'pressure' surge cycles.

The subject accumulators are val-uable'a-s-'=hy= drau lic power" reservoirs and areparticularly valuable .to absorb andd-i'ssipate hydraulic surge. In this latter sense they can be called acewators," but with the understanding that'they store up surge fluid and feed it back intothe system rather than bleeding itch to a'reservoir. More broadly, the present inventioncan "be-used in any installation wherein a-'- commercial bag, diaphragm, bellows, pistonor' other-type-accinnulator or' water hammer arrest'er is now being used with beneficial results flowing-from it's proved structure.

Theoperationof the present invention for example inan oil-hydraulicpneumatic system may ice-briefly described.- as follows: The accumulator is assembled into the hydraulicsystem in a substantially vertical position. It will operate-in any position but piston types aswellas all others drain best and aremOst-efiicient iftheoil port is down. In all bag and diaphragmtypes the heaviest fluid should be on the bottom and'hence the airport shouldbe atthe top. All air isble'd from the hydraulic system andthe hydraulic pressure then reduced tozero. Gas;- suchasgfor example, nitrogen (desiccated) is put, under pressure, into the accumulator through thevalve38 and pipe 3?. This gas pressure forces'thepiston l3 down to its lowermost position which "forces practically all fluid out ofrthe unit. Theprel harge gas pressure is then built upito some predetermined value usually between one-thirdiand one-half or the probable working pressure ofithe system. The valve 38 is then closed: an dft'he-hydraulic pressure is turned on As the pressure in the system buildsup to its worlzi'ngvalue, oil enters .the accumulator through'the ioilmports. 66 and againstth'e piston lil which. is, movedfup; wardlyiagainst the gas pressure .until thegasiand voilsp essuresrare-,equalized-., Thelpiston ltlstops movingawhen.thalineworking pressure is reached and thee-subsequent smaller volume variations, engendered by. pumpgoutput fluctuations orthe system..-.va-lves,=, are :absorbedby "reciprocal-Immemerit of- ?tha-d-iaphragm.

Ifi ai'further :majon pressure changetal res place causedrby a surge :volume. of fluid g-reater" than carrbe handled .rbyymov mentor thewdiaphragm alone;;, or-. byg'a ch'a-nge: 1 itheeopera-ting pressure of: theisystem; their the: piston is moved: to anew position anduthe systemucontinues' tooperate-at eitherr'a: higher or lower average: pressure-level than before-rwithsthex diaphragmcstill. 1 vibrating with;smallasurges: as before. This accumulator may beradaptedifcr use-anyhyd rauli'c system to handle.-= any resulted. fluid: below the piston and cushioned; against a. suitable gas above the piston.-;

Whila. the zparticular: apparatus :hereirr shown and .describediih detaiLis iullyz'capablexof attaining: the? objects and providing the advantages hereinbefore: stated, itis. to be. understood thatzit isim'erely: illustrative; of the; presently preferred embodimentsof my'inyention, and that I do not mean toilimitzmyse'lfito;therdetails. of construe trorrordesign: hereinrshown, other than *as definedi'rr'theappendeddaims:

1. A pneumatic hydraulic-accumulator comprising ::a;:tubuiar body-with closed end's; a pistonzzpositionedr WifiiiilY-Sflid' body 1 for limited slid.- in'gzmotiorrt therein, and contacting th'e wall of said: body? whereby to hermetically divide said body: into two chambers, one "of said chambers being parted wherebyto b'e 'precharged withgas and the otherof 'said chamb'ers having inlet means te -receive varying quantities of liquid; a diaphragm said -pis'ton exposed-on one side to'said gas chamber and on 'the other tosaid liquid chamber; and means-in saidbodyfor supporting said diaphragm-' when said piston approachesa limit of said motion thereof.

2 pneumatic hydraulic accumulator" comprising: a tubularbodywitn closed ends; 'a pieton: positioned withirrsaidbody for limiting slid-'- ing motion-therein; and con-tacting the wall of said body whereby" to hermetically divide said bod-Y into'two cha-mbers; one of said chambers being parted whereby, to be prechargedwith gas; afsecond -p'ort' in saidb'ody adapted'to supply liquid under pressure to the. other'of said chambers; adiaphragm transversely disposed'and secured in-sai-d piston,v exposed-on onesi'de'to said gas chamber and ontheother to said liquid chamber; said"diaphrag1nfbeingflexible to permit axialmotion' relative to said' piston; and mean'sfit'or" supporting saiddiaphragm when the pressure of saidliquid is; less thansaidprecharged gas pressure.

A, pneumatic 'hydraulic accumulator coinpri'singzg a tubular hody'with' closedends'; apiston-"positioned. within said body adapted for um! ited'sli'ding motion therein, andhermeticallyidi vidingsaid. 'bodyfintoi two" chambers, one oifisaid chambers: being adapted to, be precharged" with gas; aport in saidiibody adapted to supplyl'iq uid unclerpressure to the: other oilsaid'. chambers; a diaphragm secured. in saidpiston ex.- posed on one side tosaidfgasichamber. and-lion the other to .said'liduidl' chamberg. andadapted for radial flexing: motioml and 'means for supporting said diaphragm when. the pressure of saidliqui'dis less than said prechargedgas pressure.

4. A pneumatic hydraulic accumulator comprising: a tubular body having closed ends; a piston slidably supported in said body and contacting the wall thereof to hermetically separate said body into two chambers, one being parted to be precharged with gas and the other connected to receive liquid; a flexible diaphragm in said piston exposed on one side to said gas chamber and on the other to said liquid chamber; means in one of said closed ends forming an inlet port for said liquid receiving chamber; and means associated with said inlet port to prevent impingement of said liquid on said diaphragm.

5. A pneumatic hydraulic accumulator comprising: a tubular body having closed ends; a piston slidably supported in said body and contacting the wall thereof to hermetically separate said body into two chambers, one being ported to be precharged with gas and the other connected to receive liquid, a flexible diaphragm in said piston exposed on one side to said gas chamber and on the other to said liquid chamber; and a plug forming one of said closed ends adjacent said liquid chamber, said plug having an inwardly extending portion positioned and shaped to support said diaphragm against damage by said precharge pressure, said extending I portion having a liquid port formed therein disposed and adapted to direct incoming fluid away from said diaphragm.

6. A pneumatic hydraulic accumulator comprising: a tubular body having closed ends; a piston slidably supported in said body and contacting the wall thereof to hermetically separate said body into two chambers, one being ported to be precharged with gas and the other connected to receive liquid; a flexible diaphragm in the top of said piston exposed on one side to said gas chamber and on the other to said liquid chamber; and a plug forming one of said closed ends adjacent said liquid chamber, said plug having an inwardly extending portion with a face on the inner end thereof shaped and positioned to support said diaphragm when said precharge pressure exceeds said liquid pressure, said extending portion having a liquid port formed therein disposed to direct incoming liquid through the side of said extending portion whereby to avoid impingement thereof against said diaphragm.

7. A pneumatic hydraulic accumulator comprising: a tubular body with closed ends; a piston positioned within said body and contacting the wall thereof for limited sliding motion therein, whereby to hermetically divide said body into two variable volume chambers, one of said chambers being ported to be precharged with gas; a diaphragm secured in said piston, exposed on one side to said gas chamber and on the other to said liquid chamber; and normally unsupported to permit limited radial flexing motion thereof; and a plug forming one of said closed ends adjacent said fluid chamber, said plug having an inwardly extending portion With sides shaped to support said diaphragm when said precharge pressure exceeds said fluid pressure, said extending portion having a fluid port forward therein disposed to direct incoming fluid axially and away from impingement thereof against said diaphragm.

8. A pneumatic hydraulic accumulator comprising: a tubular body having closed ends; a piston slidably positioned within said body to divide said body into two chambers, one to receive gas and the other to receive liquid; sealing means in said piston positioned to make a slidable fluid seal against said tubular body; a flexible diaphragm in said piston exposed on one side to said gas chamber and on the other side to said liquid chamber; and a plug forming the closure of the liquid receiving portion of said body and comprising a central body portion, an inwardly extending portion having a surface thereon substantially complemental to said piston, said plug having a port formed therein adapted to connect said liquid chamber to a source of liquid, said port being disposed and positioned to be covered by a non-flexible portion of said piston when said precharged gas pressure exceeds said liquid pressure.

9. A pneumatic hydraulic accumulator comprising: a tubular shell having closed ends, one of said ends having a port therein to receive a gas, and the other of said ends having a port therein to receive varying quantities of liquid; a piston slidably positioned within said shell between said closed ends and sealably dividing the space within said shell into a gas chamber and a liquid chamber; and a diaphragm in said piston open on one side to said gas chamber and on the other side to said fluid chamber, said piston being movable in said shell and said diaphragm being movable with respect to said piston to compensate for relative volume variations between said gas and said liquid chambers.

10. A pneumatic hydraulic accumulator which includes; enclosure means forming a gas chamher and an adjacent liquid receiving chamber, said chambers having a plurality of common wall sections separating said chambers from each other and movable in response to difierential pressures in said chambers; one of said wall sections being deformable to respond to minor pressure differentials between said chambers, and another of said sections being displaceable in response to major pressure differentials to equalize the pressure between said chambers whereby said first section is responsive to pressure differentials at all working pressures in said chambers; and means for connecting said liquid receiving chamber to a source of liquid subject to variable pressure.

11. A pneumatic hydraulic accumulator comprising: a tubular body with closed ends; a piston slidably positioned within said body and having fluid tight contact with the walls thereof whereby to hermetically divide said body into two chambers of dependently variable volume; and a diaphragm secured in said piston exposed on one side to said gas chamber and on the other to said liquid chamber; said diaphragm being movable with respect to said piston whereby to permit relative volume variations between said two chambers without movement of said piston and port means for introducing gas into one of said chambers and liquid into the other.

12. In a pneumatic hydraulic accumulator: a fluid tight enclosure; a plurality of spaced fluid connections in the wall of said enclosure to admit gas and liquid into said enclosure; and internal separatory means in said chamber adapted to separate said gas and liquid, said separatory means including at least two wall sections having fluid tight contact with the wall of said enclosure, one of said wall sections being slidable to vary the relative volume of said gas and liquid in said enclosure, and the other of said wall sections being movable independently of motion of said first section to vary said relative volumes, said wall sections having substantially diiierent resistance to motion.

13. In a pneumatic hydraulic accumulator,

the combination of: a cylinder closed at its ends; a piston slidable in said cylinder in sealing engagement therewith whereby to form a plurality of chambers therein; means for admitting gas into one of said chambers; means for connect; ing the other of said chambers to a source of pressure liquid; and a diaphragm movable with respect to said piston and having one of its faces open to the gas in said gas chamber'and its other face open to said pressure liquid, whereby said diaphragm and said piston are differentially responsive to variations in pressure of said gas and said liquid.

14. In a pneumatic hydraulic accumulator,

the combination of enclosure means forming a 5 chamber; means for admitting gas to said chamber; means for admitting liquid under variable pressure to said chamber; and two differentially 14 movable wall sections in said chamber dividing the same into gas and liquid compartments, said wall sections being differentially responsive to variations in the pressures of said gas and liquid, one of said wall sections being readily responsive to small pressure changes and the other Wall section being responsive only to relatively larger pressure changes.

ROBERT E. SNYDER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,365,994 Ashton Dec. 26, 1944 2,406,197 Christensen Aug. 20, '1946 2,417,256 Kremiller Mar. 11, 1947 

